Which of the following formulae is used to determine the compressibility factor $(Z)$ for the measurement of deviation from ideal behavior?

$A$ gas is said to behave like an ideal gas when the relation $PV/T = \text{constant}$. When do you expect a real gas to behave like an ideal gas?

Consider the following gases and their corresponding $ 'a'$ values given in parentheses: $CH_4 (2.25), N_2 (1.35), O_2 (1.36)$,and $CO (1.46)$. Which of these gases will be the most difficult to liquefy?

The units of constant $a$ in the Van der Waals equation are:

Given van der Waals constant $a$ for $NH_{3}$,$H_{2}$,$O_{2}$ and $CO_{2}$ are respectively $4.17$,$0.244$,$1.36$ and $3.59$,which one of the following gases is most easily liquefied?

At a given temperature $T$,gases $Ne$,$Ar$,$Xe$,and $Kr$ are found to deviate from ideal gas behaviour. Their equation of state is given as $P = \frac{RT}{V - b}$ at $T$. Here,$b$ is the van der Waals constant. Which gas will exhibit a steeper increase in the plot of $Z$ (compression factor) versus $P$?